Here you can find the source of _peek()
Array.prototype._peek = function(){ if(this.length > 0) return this[this.length - 1]; return null; };// w ww . ja va 2 s. com
Array.prototype.peek = function () { return this[this.length - 1]; };
Array.prototype.peek = function(){ if (this.length > 0){ return this[this.length - 1]; } else { return null;
Array.prototype.peek = function() { var index = Math.floor(Math.random() * this.length); return this[index]; };
Array.prototype.peek = function(index) { if(!index) index = 0; return this[this.length - index - 1];